Ok, if you know how to autostack burrowable units with triggers, like keep moving them to unmoveable terrain, there's a problem - if you an enemy walk by your stacked units, they will attack it. But, if the enemy leaves your units, they will still be targetting that enemy. If another enemy walks by, your units will not attack it, because they are still "attacking" the other enemy. To stop this freezing, you have to make your units hold position. However, that's a pain to do, and if you have many units stacked, it's hard to pick the ones not holded and make them hold.
So what I'm asking is: Is there any way to autostack without having the units hold positoin or freeze?
If you're stacking, wouldn't they be in one spot by definition?
You could have it center on each location, give them all to another player, continue, then give them all back.